Most of the DirectDraw functionality is implemented in a common base
class. Derived classes are responsible for providing display
mode functions (Enum, Set, Restore), GetCaps, GetDevice identifier
and internal functions called to create primary and backbuffer
surfaces.
User provides for DirectDraw capabilities based on drawing to a
Wine window. It uses the User DirectDrawSurface implementation
for primary and backbuffer surfaces.
XVidMode attempt to use the XFree86 VidMode extension to set the
display resolution to match the parameters to SetDisplayMode.
DGA2 attempt to use the XFree86 DGA 2.x extension to set the
display resolution and direct access to the framebuffer, if the
full-screen-exclusive cooperative level is used. If not, it just
uses the User implementation.
